The invention relates to polymer foams. In particular, the invention relates to polymer foams having low densities with enhanced physical properties.
Foam structures are useful in the areas of packaging, athletics, water sports, and construction. In general, the foams are low density polymeric materials with good physical properties that are capable of supporting loads without adverse deformation. In general, the physical properties required by these applications suggest the use of high density foams. It is generally required that the foams have good proportional limit, compressive properties, shear properties, fatigue properties, and buckling limits, as defined, for example, in "Machinery's Handbook," E. Oberg, et al., Green, Ed., Industrial Press Inc., New York, 1992, pages 166, 168 and 253.
Physically-blown foams, particularly foams with enhanced physical properties are useful, for example, in packaging, automotive, construction, contact sports, water sports, exercise, and appliance applications. It is important to maintain good foam properties (e.g., cushioning and resistance to creasing) at low foam densities.
Packaging design has focused on the use of systems such as end caps which fit on opposite ends of the packaged product (e.g., televisions, computers, and electronic equipment, or high value artifacts such as glass vases or fragile art work) and suspend the product in the center of a container during shipping and storage. Previous suspension-type packaging systems have been composed of corrugated or paperboard materials, molded low density foams such as polystyrene, protective films or sheeting, wood, plastic, organic or inorganic fill, or combinations of the above materials that are glued together. Molded packaging materials, such as styrofoam end caps, are bulky to transport and store. It is most desirable for the structure to provide the required packaging protection with the lowest amount of added weight.